This method and the IetfLanguageTag property are deprecated. Instead of using these elements, the application should use a new CultureInfo object and calls to the Name property. IETF tags and names are identical.

The RFC 4646 standard that is maintained by the Internet Engineering Task Force (IETF) defines an IETF language tag, which provides a uniform means of identifying a language. The format of an IETF language tag is the same as the culture name returned by the Name property, but does not identify a culture uniquely. Different cultures share the same IETF language tag if those cultures have identical linguistic characteristics. The linguistic characteristics of a culture are contained in the TextInfo object associated with a CultureInfo object.

An IETF language tag consists of a mandatory language identifier, an optional script identifier, and an optional region identifier.

Your applications should use the retrieved culture to control language-specific tasks, such as managing a spelling or grammar checker. Applications should not use the retrieved culture to control culture-specific tasks, such as sorting text or formatting times and dates.

The .NET Framework 3.5 and earlier versions throw an ArgumentException if name does not correspond to the name of a supported culture. Starting with the .NET Framework 4, this method throws a CultureNotFoundException.